Chronic obstructive pulmonary disease (COPD) is a disease of the lungs in which the airways narrow over time limiting airflow into and out of the lungs causing shortness of breath. In most cases, advanced stages of COPD may lead to breathing difficulties caused by the inability of the lungs to inflate/deflate due to severe air trapping. One type of COPD is emphysema in which the airways distal to the terminal non-respiratory bronchioles enlarge due to the breakdown and destruction of the alveolar walls. Emphysema can result in air trapping, hyperinflation, and dynamic hyperinflation, each of which may reduce a patient's ability to respire. This reduction in a patient's ability to respire may ultimately lead to respiratory failure. In essence, in emphysema patients, the residual volume of the airways distal to the terminal non-respiratory bronchioles increases significantly, leaving little remaining room in their thoracic cage to breath.
COPD is most commonly caused by noxious particles or gas, often from tobacco smoking, which triggers an abnormal inflammatory response in the lung and which may damage or destroy lung tissue. Conventionally, Lung Volume Reduction Surgery (LVRS) has been used to remove diseased and/or emphysematous lung tissue, thereby allowing the expansion of the remaining (e.g. healthier) portions of the lung tissue. This procedure is possible because the lungs are divided up into relatively independent functional units. Specifically, the lungs are divided up by fissures into a predictable arrangement of lobes. For example, a human right lung includes three lobes—a superior lobe, a middle lobe, and an inferior lobe. A human left lung includes two lobes—a superior lobe and an inferior lobe. The lobes are characterized by a discrete connection with the first subdivision of the bronchial tree after the level of the principal bronchi to both lungs—the lobar bronchi. In a similar manner, the vascular, nerve, and lymphatic supply from the hila to each lobe has minimal connection with other lobes. This makes the lobes relatively independent functional units within the lung. Indeed, pathology may be confined to one lobe and corrective surgery may be facilitated by the clear demarcation between lobes produced by the fissures.
Contrary to intuition, LVRS has been shown to help improve breathing ability, lung capacity and overall quality of life. The healthy alveoli are able to inflate more fully and dead space is reduced. LVRS, however, may cause extensive discomfort to patients, and may pose serious health risks due to the invasive nature of the procedure. Lung transplantation is another surgical treatment for homogeneous (diffuse) emphysema. However, lung transplantation suffers from similar drawbacks as LVRS and may be an unrealistic option for most patients as lung transplant eligibility is limited both by stringent patient selection criteria and the scarcity of donor lungs.
Therefore, a need exists for a minimally invasive treatment that selectively controls air flow into the lungs to allow expansion of healthier portions of the lungs.